Malaria was eradicated in the United States in the 1950s, however it is still common in many developing countries. If your travel plans take you to tropical or subtropical countries in Africa, Asia, the Middle East, South America and Central America, make sure you go prepared with a prescription antimalarial medication and an effective insect repellent. The World Health Organization estimates that 300 to 500 million cases of malaria occur worldwide each year, causing more than 1 million deaths annually.

Malaria is an infectious disease caused by a parasite that is transmitted by mosquitoes. (It is not transmitted from person to person like the flu or a cold, and you cannot contract it through casual contact with someone who is infected.) Most cases of malaria in the United States develop in travelers who have recently returned from arts of the world where the disease is widespread.

Signs and symptoms of a malarial infection include recurrent episodes of moderate to severe shaking chills, high fever, flu-like symptoms, profuse sweating, muscle aches and fatigue. Other symptoms include headache, nausea, vomiting and diarrhea, and because malaria attacks red blood cells it can also cause anemia and jaundice (yellow coloring of the skin and eyes).

Generally, people contract malaria after being bitten by an infected female anopheles mosquito. (The mosquito becomes infected with the disease after having bitten someone who was already infected; and so the disease is carried on.) The mosquito bite injects microscopic parasites into the bloodstream, where they continue to multiply and infect the red blood cells. This means that malaria can also be transmitted through blood transfusions, organ transplant or the use of hared needles and syringes, which is one reason that donors are carefully screenedfor malaria before blood or organ donation. It also means that a pregnant woman who is infected with malaria can pass the disease to her baby during pregnancy or delivery.

The Plasmodium falciparum type of malaria, most often found in sub-Saharan Africa, is the most severe and presents the greatest risk of fatality. Complications of P. falciparum malaria include severe anemia, swelling of the brain or brain damage. Other complications include pulmonary edema (fluid in the lungs), dehydration, liver failure, kidney failure and rupture of the spleen. If untreated, P. falciparum malaria can be fatal within a matter of hours.

In most cases, however, because symptoms generally appear 10 days to four weeks after the initial mosquito bite — although they can appear as early as eight days or as late as one year later — travelers might not realizeimmediately that they have been infected. That’s why it is wise to take precautions to avoid contracting the disease. Currently, there is no vaccine approved for human use to prevent malaria, however there are antimalarial medications that can be taken before and during a trip to help reduce the risk of infection. Applying insect repellent to the skin and clothing can also elp to keep diseasecarrying mosquitoes at bay.

If you do become infected, malaria should be treated as early as possible. Seek professional medical care, and make sure to tell your physician that you have visited a malaria-risk area, even if your visit took place months before symptoms appear. In general, if you are treated correctly for malaria, the parasites are eliminated and you are no longer infected with the disease.

For more information, visit http://www.nih.gov.

Be Prepared

Before you travel:

Visit a physician 4 to 6 weeks before foreign travel for necessary vaccinations and a prescription for an antimalarial drug.

Fill the prescription in the United States, since drug quality varies worldwide.

Take the antimalarial drug as directed by the physician.

Prepare a list of your prescription medications, including manufacturer, brand name and generic name, to carry with you so you can refill or replace them if necessary.

While you’re away:

Use an insect repellent containing DEET on exposed skin to repel mosquitoes.

DEET concentrations of 30 to 50 percent are effective for several hours. DEET formulations as high as 50 percent are recommended for both adults and children older than 2 months.

Protect infants younger than 2 months in a carrier draped with mosquito netting that is secured with an elastic edge.

Apply insect repellents that contain permethrin to clothing, shoes, tents, mosquito nets and other gear for greater protection. Permethrin-treated fabric will remain effective through five washings. Note: Permethrin is not intended for use directly on skin.

Stay in air-conditioned or well-screened housing, especially at dawn, at dusk and in the evening when mosquitoes that transmit malaria are most active.

Sleep under an insecticide-treated bed net with its edges tucked under your mattress.